1. Field of the Invention
The present invention relates to a magnetic video recording apparatus which is adapted to be applied to, for example, a video tape recorder (VTR) provided with a detachable television camera.
2. Description of the Prior Art
In the conventional video tape recorder, it is customary to employ signal correction circuits such as an AGC (automatic gain control) circuit, an ACC (automatic chroma control) circuit and so forth for correction of the input video signals before recording.
FIG. 1 shows a conventional video tape recorder 1 as a whole wherein a luminance signal Sy is supplied to an AGC circuit 2, while a chrominance signal Sc is supplied to an ACC circuit 4 via a band-pass filter circuit 3.
The AGC circuit 2 and the ACC circuit 4 correct the levels of the luminance signal Sy and the chrominance signal Sc respectively to predetermined signal levels and supply the output signals to an equalizer circuit 6 and a burst emphasis circuit 7, respectively.
Thus, the AGC circuit 2 and the ACC circuit 4 constitute correction circuits which correct levels of the luminance signal Sy and levels of the chrominance signal Sc of the resultant composite video signal.
A record signal processing circuit 8 receives the luminance signal Sy derived from the equalizer circuit 6 and, after processing the same through white clipping and dark clipping stages, supplies the processed signal via an FM (frequency modulation) circuit 9 to a mixer circuit 10.
Meanwhile, a low-frequency converter circuit 12 receives a local oscillation signal S.sub.Lc together with the chrominance signal Sc derived from the burst emphasis circuit 7 and, after converting the chrominance signal into a lower frequency signal band, supplies the converted chrominance signal via a low-pass filter circuit 13 to the mixer circuit 10.
In this manner, the frequency-modulated luminance signal and the frequency-converted chrominance signal are obtained via the mixer circuit 10 and then are recorded on a magnetic tape 16 by way of a record current amplifier circuit 14 and a magnetic head 15.
Consequently, even when the luminance signal and the chrominance signal have errors as compared with the standard signal levels due to the influence resulting from some transmission loss or variation in the video appliance that supplies such luminance signal and chrominance signal, it becomes possible, by means of the AGC circuit 2 and ACC circuit 4, to correct both the luminance signal and the chrominance signal to the predetermined signal levels respectively, in order to achieve satisfactory reproduction of the video signal with a high image quality.
The video tape recorded of the type mentioned above is provided with a detachable television camera and functions to record the video signals derived therefrom as well as to record the video signals derived from some other video appliance such as a television receiver.
When the above-described video tape recorder is operated for recording the video signals derived from a television receiver or the like, since there may exist a possibility that the input video signals have some level errors in comparison with reference levels, the respective levels of the luminance signal and the chrominance signal are corrected by means of the AGC circuit 2 and the ACC circuit 4 so that satisfactory video reproduction can be performed with a high image quality.
However, in recording the video signals derived from the television camera detachable from the VTR, the AGC circuit 2 and the ACC circuit 4 equipped in the VTR are used without necessity if the output signal level of the television camera is adjusted exactly to its predetermined reference level. The unnecessary use of the AGC and ACC circuits deteriorates the signal to-noise ratio of the video signal.